1) Its implied that plate tectonics suppress carbon which is the reason Venus has a high CO2 atmosphere and is hot. But it also said the hot temp is why Venus didn't develop plate tectonics in the first place. Is there a chicken/egg issue here?

2) Saying plate tectonics is the reason for life 3 billion years later seems off as life developed on earth 1-2 billion years after it formed.

3) I remember reading a theory that the smashing of the earth to create the moon might've imparted energy to cause tectonics to happen. Any effect from that?

I suppose the next step is to carry the modelling forward in time; will Venus develop plate tectonics in the future? On the one hand, as it ages the Sun is slowly getting more luminous; this will result in a hotter atmosphere and hotter surface temperature, which in turn should mean a hotter upper crust. On the other hand as radioactives decay, Venus' internal temperature will drop resulting in the lower layers of the crust warming up less rapidly with increasing depth. Which trend will dominate, and will it eventually result in Venus' crust breaking into plates?

2) Saying plate tectonics is the reason for life 3 billion years later seems off as life developed on earth 1-2 billion years after it formed.

I think the point here is that tectonic action is considered potentially necessary for life, but is not sufficient for life.

And the reason why it's considered potentially needed for life is that by burying carbon in the mantle it allows a steady decline in greenhouse gas levels over time which by countering stars increase in luminosity over time extends the period a planet can remain within a temperature band suitable for complex life.

1) Its implied that plate tectonics suppress carbon which is the reason Venus has a high CO2 atmosphere and is hot. But it also said the hot temp is why Venus didn't develop plate tectonics in the first place. Is there a chicken/egg issue here?

I too thought this was a bit of an odd way to explain it.

Cycling carbon isn't so much about keeping carbon out of the atmosphere. After all when carbon is being subducted it already isn't in the atmosphere. What it does though is allow a process that DOES take carbon out of the atmosphere to never entirely scrub the atmosphere. So now you have moderation. Neither carbon getting locked up for all eternity or run-away CO2 like Venus (until earth cools enough to no longer have volcanoes/subduction because the crust is too thick for the layers below it to move it).

2) Saying plate tectonics is the reason for life 3 billion years later seems off as life developed on earth 1-2 billion years after it formed.

I think the point here is that tectonic action is considered potentially necessary for life, but is not sufficient for life.

And the reason why it's considered potentially needed for life is that by burying carbon in the mantle it allows steady decline in greenhouse gas levels over time which by countering stars increase in luminosity over time extends the period a planet can remain within a temperature band suitable for complex life.

Which is one of the complex set of criteria that whittles down the habitable planet set for carbon-based life-forms. Still will mean there are some other planets out there with carbon-based life-forms, but instead one in every few million, it may be one in ever hundreds of billions.

I wouldn't consider plate tectonics essential for life in general. I could see it essential for diversity of life however. Now having active an active geological profile on the other hand (volcanism, hot spots, etc.) that can move minerals around probably are, at a minimum, necessary if tectonics aren't available.

All of the other implications could be remedied by many other processes. Carbon could be sequestered by unique kinds of life and geological processes that we simply don't have on Earth for example. Life tends to evolve and adapt to fit the mold of its environment when possible.

1) Its implied that plate tectonics suppress carbon which is the reason Venus has a high CO2 atmosphere and is hot. But it also said the hot temp is why Venus didn't develop plate tectonics in the first place. Is there a chicken/egg issue here?

Venus receives something like 93% more solar energy than the Earth due to its proximity to the Sun, so it was already starting at a higher baseline temperature, a temperature that was hot enough to induce the runaway greenhouse effect and raise the temperature even more.

1) Its implied that plate tectonics suppress carbon which is the reason Venus has a high CO2 atmosphere and is hot. But it also said the hot temp is why Venus didn't develop plate tectonics in the first place. Is there a chicken/egg issue here?

There are multiple reasons why Venus is the way it is.

1) Venus gets about 91% more solar energy than Earth does. This makes it hot.2) Venus's solar day is approximately 115 Earth days long. This makes it even more hot on the side facing the sun.3) There is no geological carbon cycle (described in this article). This prevents "fresh" rock from absorbing carbon.4) Because of the lack of plate tectonics, volcanism is far more prevalent on Venus than on Earth. This releases more CO2 into the atmosphere.5) There is no biological carbon cycle (which is far, far stronger than the geological one).6) After the rock itself, water is Earth's biggest carbon reservoir. Due to the feedback loop of 1-4, Venus became too hot for water to exist, it all evaporated (which made Venus even hotter), was photodissociated, and the Hydrogen was blown away by the solar wind.

Among other reasons that I don't really understand as well as I want to. Essentially, it boils down to Venus starting out very, very similar to Earth, but being tilted just past the point where an Earth-like system could develop. This caused a series of positive-feedback loops that kept growing, and at critical points in the planet's history it ended up being on the wrong side of the decision tree, which just made things worse.

Do we know if Venus had a similarly large bombardment? Is it not plausible that the collision with the mars sized planetoid, creating the moon, also help to issue the plate movements?

A big impact is the current least bad theory for Venus' retrograde spin; AFAIK we don't know of any other mechanism capable of either causing it to start spinning backwards or to flip its axis of rotation by ~180 degrees (which would have the same effect); but modelers haven't figured out how to generate a hit big enough to do that without creating a large moon out of the debris that the hit would create.

Article seems to me odd also. Carbon cycle is that bacteria take carbon from the air pushed into carbonates (shelled) and hydrocarbons (soft shelled). Over millions/billions of years this adds up to a low carbon atmosphere, recycling carbon keeps CO2 at reasonable levels. Life did not make Venus a CO2'less cold place, as when runaway bacteria made earth an ice ball for a few million years - early in life on this planets history.

IMO, a very radioactive core is more important to the forming life. A constant differential of energy is required to kick start it. Constant turmoil made life possible. Complex life comes from making hiding places and predators can have only one kind of opener. Allows the proliferation of life.

The explanation of why earth has plate tectonics but not Venus is very cool. Extending that to CO2 levels, not so much. In fact, one might also argue the opposite: Plate tectonics effectively recycles all that carbon sequestered on the sea floor back to the atmosphere. That being said, I think it is a stretch in any direction to connect plate tectonics, or lack thereof, to the differential in atmospheric CO2.

As stated by dferrantino above, there some other more significant factors contributing to Venus's high carbon concentration in the atmosphere (chemical, primarily due to lack of water and, of course, lack of any biological cycle).

The findings on Venus's (lack of) plate tectonics reported here is very cool! This article just seems to be a little misleading as to the magnitude of its effect on the concentration of carbon in Venus's atmosphere...

4) Because of the lack of plate tectonics, volcanism is far more prevalent on Venus than on Earth. This releases more CO2 into the atmosphere.

Not sure about the tense "is"? We haven't been able to confirm there is any current magma releases occurring.

We have confirmed that a great deal of Venus is covered with lava flows, [inactive, defunct] volcanos, etc. An absolutely massive lava flow appears to have occurred about 1/2 billion years ago (estimate based on meteor craters). There is even some evidence of relatively recent activity at the highest volcano on the planet, but not confirmed that anything is happening right now.

However remember that on Earth, in no small part because of water/rain, we have a lot more erosion that breaks down and covers our old volcano history.

Could have sworn the last "theories" I heard, said the moon creation impact was one of the biggest motivators of our crust having tectonic plates that shift and the pull of the moon on the earth also effects these points on earth too, along with affecting the Tides.

Does anyone else wonder if the majority of Earth-like exoplanets we're discovering will wind up being as inhospitable as Venus?

These models are very important, because we need to push forward to identifying the prevalence of Earth-like planetary environments. This is drastically different, and dramatically more difficult than the current stage we're on - which is just identifying the orbital parameters of the exoplanets within our neighborhood.

Oxygen gas, for instance, is often thought to be unlikely without life. I don't hold much hope of finding a planet with a similar atmosphere to Earth for this reason. But put that aside, what chances might we have of finding some N2 and methane atmosphere with the same ballpark of sea-level pressure that Earth has? What about one with water/oceans? These questions are fascinating, and represent extremely active science. You could identify the year by the number of confirmed exoplanets, because it's changing that rapidly.

Even if a planet is water-rich, that doesn't necessarily mean the the surface has hospitable temperature or pressure. These are questions I really really want to know the answer to.

Several points I find confusing:........3) I remember reading a theory that the smashing of the earth to create the moon might've imparted energy to cause tectonics to happen. Any effect from that?

Others have commented on the other points for what they are worth but I felt I should comment on this.

You shouldn't put too much stock in another article you read or even this one. These are ideas that are being tested. They both could be right one could be wrong or both could be wrong. I am familiar with the the other articles as well. Both ideas are supported by their respective models but one explains earth and the other explains Venus. It could be that Venus doesn't have plate tectonics because it has no moon or this model could explain both Venus and Earth.Working together can be a good thing. However I like it when scientist work on competing ideas separately. It helps build a more complete picture of the universe.

When I was at JPL, and prior to Magellan, we used to argue if Venus had tectonics. Magellan laid that to rest in the 90s. Continental sized subduction (massive resurfacing) is what the Magellan showed us.

Granted, we're still pretty self-centered on this Earth-centric model of life, but scientists over the years have cautioned us that nothing says that "this is the way it's gotta be." Sure, we've got a pretty good blueprint going on here. I mean it sort of works and all, but that doesn't mean it's the only "life", right?

Do we know if Venus had a similarly large bombardment? Is it not plausible that the collision with the mars sized planetoid, creating the moon, also help to issue the plate movements?

A big impact is the current least bad theory for Venus' retrograde spin; AFAIK we don't know of any other mechanism capable of either causing it to start spinning backwards or to flip its axis of rotation by ~180 degrees (which would have the same effect); but modelers haven't figured out how to generate a hit big enough to do that without creating a large moon out of the debris that the hit would create.

I thought the current favored theory was something to do with tidal effects on Venus and its atmosphere from the Sun? I remember reading about that, at least.

So you're saying that if we figured out how to throw one of the larger asteroids from the belt beyond Mars, at Venus, maybe we could turn it non-Newtonian enough to live on?

If the Earth's plate tectonics are due to the collision that created the moon, we'd need to throw Mars at Venus to create a similar size impact. Afterward, we'd need to use the same handwavium powered planet mover employed to shove Mars inward fast enough to avoid disrupting the Earth's orbit by a close pass to deflect the huge number of planetary fragments scattered around the inner solar system from hitting the Earth and causing an extinction level impact.

So you're saying that if we figured out how to throw one of the larger asteroids from the belt beyond Mars, at Venus, maybe we could turn it non-Newtonian enough to live on?

If the Earth's plate tectonics are due to the collision that created the moon, we'd need to throw Mars at Venus to create a similar size impact. Afterward, we'd need to use the same handwavium powered planet mover employed to shove Mars inward fast enough to avoid disrupting the Earth's orbit by a close pass to deflect the huge number of planetary fragments scattered around the inner solar system from hitting the Earth and causing an extinction level impact.

Assuming some sort of handwavium powered planet moving device, as a thought experiment, what would happen if we slammed Mars into Venus and then dragged the resulting.. whatever is left into orbit 90 degrees off Earth's orbit (or 180 off, but I figure we'd want to be able to see it.)

So you're saying that if we figured out how to throw one of the larger asteroids from the belt beyond Mars, at Venus, maybe we could turn it non-Newtonian enough to live on?

If the Earth's plate tectonics are due to the collision that created the moon, we'd need to throw Mars at Venus to create a similar size impact. Afterward, we'd need to use the same handwavium powered planet mover employed to shove Mars inward fast enough to avoid disrupting the Earth's orbit by a close pass to deflect the huge number of planetary fragments scattered around the inner solar system from hitting the Earth and causing an extinction level impact.

Assuming some sort of handwavium powered planet moving device, as a thought experiment, what would happen if we slammed Mars into Venus and then dragged the resulting.. whatever is left into orbit 90 degrees off Earth's orbit (or 180 off, but I figure we'd want to be able to see it.)

If you have the technology to move a planet to a desired position, I'd think that terraforming would be trivial.

Does anyone else wonder if the majority of Earth-like exoplanets we're discovering will wind up being as inhospitable as Venus?

These models are very important, because we need to push forward to identifying the prevalence of Earth-like planetary environments. This is drastically different, and dramatically more difficult than the current stage we're on - which is just identifying the orbital parameters of the exoplanets within our neighborhood.

Oxygen gas, for instance, is often thought to be unlikely without life. I don't hold much hope of finding a planet with a similar atmosphere to Earth for this reason. But put that aside, what chances might we have of finding some N2 and methane atmosphere with the same ballpark of sea-level pressure that Earth has? What about one with water/oceans? These questions are fascinating, and represent extremely active science. You could identify the year by the number of confirmed exoplanets, because it's changing that rapidly.

Even if a planet is water-rich, that doesn't necessarily mean the the surface has hospitable temperature or pressure. These are questions I really really want to know the answer to.

I know a lot of them that the media has been crowing about as "earth's twin" have been around 3 times more massive (because these are easier to see than earth size objects they get found at a higher rate). So rocky in the goldilocks zone = earth's twin. I don't know about you guys, But I'm not signing on for a trip where when I reached the destination (assuming I don't die of old age first) I weigh between 600 and 900 lbs. At least this one is the twiniest they have found so far, at roughly the same mass and rocky. Doesn't mean it doesn't have some other weird problem for life like we have on earth (15% arsenic crust or some such to just pull something I have no idea about the plausibility of out of my bum).

2) Saying plate tectonics is the reason for life 3 billion years later seems off as life developed on earth 1-2 billion years after it formed.

I think the point here is that tectonic action is considered potentially necessary for life, but is not sufficient for life.

I think the argument goes more or less like this. Without plate tectonics carbon, and also other necessary elements for like like phosphorus, end up stuck at the bottom of the ocean and buried forever. Eventually the oceans fill up with the stuff, meanwhile the atmosphere fills up with whatever is being pumped out by volcanoes. There is no 'closed loop' because no transport back INTO the mantle exists to both remove stuff that comes out from volcanoes and free up stuff that is stuck in the sediments at the bottom of the ocean (melt it and send it back up in said volcanoes where it returns to the biosphere). The end result is there isn't an equilibrium. Life might get started on such a world, but sooner or later the whole planet will wander off into some dead end state like Venus, Mars, etc.

The thing is, life depends on a DYNAMIC equilibrium, one where stuff is moving around. Venus or Mars have equilibrium, but it is a largely static one where nothing changes or happens. Different elements tend to end up sequestered forever in the least available (most stable) forms, and life can't get at them. Conditions also tend to be driven to extremes. Earth's dynamic balance exists because the surface is hooked into a much longer term and more energetic cycle that is happening beneath the crust. Its a bigger and more robust system due to this coupling and one where things get mixed up constantly.

2) Venus's solar day is approximately 115 Earth days long. This makes it even more hot on the side facing the sun.

Actually--and interestingly--there is almost no difference in temperature between the day and night sides of the planet. Day or night, the heat doesn't leave.

Which is also why Venus (day side or night side) is hotter than the day side of Mercury.

It is NOW. The theory is that there would have been a time when Venus had an atmosphere more like Earth's, before runaway greenhouse cooked it to a 100x more massive CO2 blanket.

Of course the Moon-forming-impact probably also blasted Earth's primordial atmosphere into space, so we don't REALLY know what the differences are. Its possible we'd be another Venus if that 'reset' hadn't happened. Plus the early Earth's atmosphere is still pretty poorly understood. We have a lot of theories but nothing that ENTIRELY matches the evidence.